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Date: Mon, 29 Aug 2016 04:25:21 +0000 (UTC)
From: "Fenghua Hu (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.12991977.1469228352000.432698.1472444721435@Atlassian.JIRA>
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References: <JIRA.12991977.1469228352000@Atlassian.JIRA> <JIRA.12991977.1469228352085@arcas>
Subject: [jira] [Comment Edited] (HDFS-10682) Replace FsDatasetImpl object
 lock with a separate lock object
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archived-at: Mon, 29 Aug 2016 04:25:23 -0000


    [ https://issues.apache.org/jira/browse/HDFS-10682?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15444774#comment-15444774 ] 

Fenghua Hu edited comment on HDFS-10682 at 8/29/16 4:25 AM:
------------------------------------------------------------

In FsDatasetImpl#FsDatasetImpl() and FsDatasetImpl#addVolume():
volumeMap = new ReplicaMap(this);
and 
ReplicaMap tempVolumeMap = new ReplicaMap(this);

"this" is used as synchronization object:

 ReplicaMap(Object mutex) {
      if (mutex == null) {
        throw new HadoopIllegalArgumentException(
            "Object to synchronize on cannot be null");
      }
      this.mutex = mutex;
  }

ReplicaMap uses synchronized(mutex) {...} for synchronization. Do we need change it accordingly?
[~vagarychen] [~arpitagarwal]


was (Author: fenghua_hu):
In FsDatasetImpl#FsDatasetImpl() and FsDatasetImpl#addVolume():
volumeMap = new ReplicaMap(this);
and 
ReplicaMap tempVolumeMap = new ReplicaMap(this);

"this" is used as synchronization object:

 52   ReplicaMap(Object mutex) {
 53     if (mutex == null) {
 54       throw new HadoopIllegalArgumentException(
 55           "Object to synchronize on cannot be null");
 56     }
 57     this.mutex = mutex;

ReplicaMap uses synchronized(mutex) {...} for synchronization. Do we need change it accordingly?
[~vagarychen] [~arpitagarwal]


> Replace FsDatasetImpl object lock with a separate lock object
> -------------------------------------------------------------
>
>                 Key: HDFS-10682
>                 URL: https://issues.apache.org/jira/browse/HDFS-10682
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: datanode
>            Reporter: Chen Liang
>            Assignee: Chen Liang
>             Fix For: 2.8.0
>
>         Attachments: HDFS-10682-branch-2.001.patch, HDFS-10682-branch-2.002.patch, HDFS-10682-branch-2.003.patch, HDFS-10682-branch-2.004.patch, HDFS-10682-branch-2.005.patch, HDFS-10682-branch-2.006.patch, HDFS-10682.001.patch, HDFS-10682.002.patch, HDFS-10682.003.patch, HDFS-10682.004.patch, HDFS-10682.005.patch, HDFS-10682.006.patch, HDFS-10682.007.patch, HDFS-10682.008.patch, HDFS-10682.009.patch, HDFS-10682.010.patch
>
>
> This Jira proposes to replace the FsDatasetImpl object lock with a separate lock object. Doing so will make it easier to measure lock statistics like lock held time and warn about potential lock contention due to slow disk operations.
> Right now we can use org.apache.hadoop.util.AutoCloseableLock. In the future we can also consider replacing the lock with a read-write lock.


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